Throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation; full citations for these documents may be found at the end of the specification. The disclosure of the publications, patents, and published patent specifications referred in this application are hereby incorporated by reference into the present disclosure.
Fillers are added to plastics for enhancement of various structural, processing and application properties. Anti-block products are normally used in the plastic films to lessen the adhesion or blocking of the plastic film surface. This can be achieved by slightly roughening the film surface through surface treatment with wax/polymers or by adding anti-block filler products into the plastic films. Commercial anti-block filler products include synthetic silica, natural silica (such as diatomaceous earth), and other mineral products such as talc, calcium carbonate, and nepheline syenite. These additives are intended to produce microscopic roughness on the surface of the film to minimize the flat contact between adjacent layers, i.e., to prevent individual layers from sticking to one another or blocking.
Although synthetic silica has good anti-block performance and optical properties, the high cost limits its applications in the plastic films. Diatomaceous earth is an effective anti-block agent with moderate cost. The anti-block performance of other mineral products such as talc, calcium carbonate, and nepheline syenite are not as effective compared to diatomaceous earth product.
Mineral fillers have been added to thermoplastic and thermoset materials to improve their properties including tensile strength, heat distortion temperature, and modulus. Besides improvement on the properties, fillers also reduce costs since the filled thermoplastics are sold in even larger volumes than neat thermoplastics.
Thermoplastic materials are those which soften under the action of heat and harden again to their original characteristics on cooling, that is, the heating-cooling cycle is fully reversible. By conventional definition, thermoplastics are straight and branched linear chain organic polymers with a molecular bond. Examples of well-known thermoplastics include products of acrylonitrile butadiene styrene (ABS), styrene acrylonitrile (SAN), acrylate styrene acrylonitrile (ASA), methacrylate butadiene styrene (MBS). Also included are polymers of formaldehyde, known as acetals; polymers of methyl methacrylate, known as acrylic plastics; polymers of monomeric styrene, known as polystyrenes; polymers of fluorinated monomers, known as fluorocarbons; polymers of amide chains, known as nylons; polymers of paraffins and olefins, known as polyethylenes, polypropylenes, and polyolefins; polymers composed of repeating bisphenol and carbonate groups, known as polycarbonates; polymers of terephthalates, known as polyesters; polymers of bisphenol and dicarboxylic acids, known as polyarylates; and polymers of vinyl chlorides, known as polyvinyl chlorides (PVC). High performance thermoplastics have extraordinary properties, for example, polyphenylene sulfide (PPS), which has exceptionally high strength and rigidity; polyether ketone (PEK), polyether ether ketone (PEEK), polyamide imide (PAI), which have very high strength and rigidity, as well as exceptional heat resistance; and polyetherimide (PEI), which has inherent flame resistance. Unusual thermoplastics include ionomers, i.e., copolymers of ethylene and methacrylic acid that have ionic rather than covalent crosslinking which results in behavior resembling that of thermoset plastics in their operating range; polyvinylcarbazole, which has unique electrical properties; and polymers of isobutylene, known as polyisobutylenes, which are viscous at room temperature.
Thermoset plastics are synthetic resins that are permanently changed upon thermal curing, that is, they solidify into an infusible state so that they do not soften and become plastic again upon subsequent heating. However, certain thermoset plastics may exhibit thermoplastic behavior over a limited portion of their useful application ranges, and are similarly useful as matrix components in applications employing the present invention. Some types of thermoset plastics, especially certain polyesters and epoxides, are capable of cold curing at room temperature. Thermoset plastics include alkyds, phenolics, epoxides, aminos (including urea-formaldehyde and melamine-formaldehyde), polyimides, and some silicon plastics.
The adhesion of the polymer matrix onto filler particles has strong impact on the reinforcement provided by the filler. The mechanical properties can be further enhanced if the polymer matrix adheres to the filler particle surface through chemical coupling agents such as silanes.
Perlite products have been prepared by milling, screening, and thermal expansion. Depending on the quality of the perlite ore and the method of processing, expanded perlite products have been used as filter aids, lightweight insulating materials, filler materials, horticultural and hydroponic media, and chemical carriers; expanded perlite has been used in filtration applications since about the late 1940's (Breese and Barker, 1994). Expanded perlite is also used as an absorbent for treating oil spills (e.g., Stowe, 1991).
Conventional processing of perlite consists of comminution of the ore (crushing and grinding), screening, thermal expansion, milling, and air size separation of the expanded material to meet the specification of the finished product. For example, perlite ore is crushed, ground, and separated to a predetermined particle size range (e.g., passing 30 mesh), then the separated material is heated in air at a temperature of 870-1100° C. in an expansion furnace (cf. Neuschotz, 1947; Zoradi, 1952), where the simultaneous softening of the glass and vaporization of contained water leads to rapid expansion of glass particles to form a frothy glass material with a bulk volume up to 20 times that of the unexpanded ore. The expanded perlite is then air separated to meet the size specification of the final product. The expanded perlite product may further be milled and separated for use as filter aid or filler material (Breese and Barker, 1994). Some degree of separation after expansion is common, for example, using cyclones, which are simple conical devices that separate particles according to their aerodynamic mass by suspending them in a stream of air. Stein (1955) states that two or more cyclones in series are sometimes used, the first cyclone having lower efficiency than the following ones, so as to air-separate the product into several size fractions. Expanded perlite products with controlled particle size distribution can be made by classifying commercial expanded perlite products (Palm, 2002, 2004). These products may be used in a variety of applications including functional filler and filter applications.
Expanded perlite products have found widespread utility in filtration applications. The principles of filtration using porous media have been developed over many years (Carman, 1937; Heertjes, 1949, 1966; Ruth, 1946; Sperry, 1916; Tiller, 1953, 1962, 1964), and have been recently reviewed in detail from both practical perspectives (Cain, 1984; Kiefer, 1991) as well as from their underlying theoretical principles (Bear, 1988; Norden, 1994).
Perlite products are applied to a septum to improve clarity and increase flow rate in filtration processes, in a step sometimes referred to as “precoating.” Perlite products are also added directly to a fluid as it is being filtered to reduce the loading of undesirable particulate at the septum while maintaining a designed liquid flow rate, in a step often referred to as “body feeding”. Depending on particular separation involved, perlite products may be used in precoating, body feeding, or both. Perlite products, especially those which are surface treated, can enhance clarification or purification of a fluid (Ostreicher, 1986).
Expanded perlite products are also often used as insulating fillers, resin fillers, and in the manufacture of textured coatings (Breese and Barker, 1994).
Particle size has strong effect on both filter aid and filler applications. The selection of the proper grade of filter aid depends on the size of the suspended particles that are to be removed. The performance of fillers is also closely related to the particle size. The anti-block performance and the film physical properties enhancement through the use of a filler strongly depend on the particle size of the filler products.
Color is also important for a filler in any application, especially where color of the end product is important. Whiter filler products with high blue light brightness normally have greater utility, as they can be used in all colored and white products and, relative to non-white fillers, improved plastic film optical properties. For these reasons, micronized perlite products with high blue light brightness are often desirable.
Oil absorption of filler products has strong impact on the plastic film processing and film quality. High absorption of resin additives such as antioxidants, slip agent and processing aid by the anti-block filler can cause serious problems during the film processing and also reduce the film quality. Therefore, low oil absorption is preferred for the anti-block filler products.
The median particle size, blue light brightness and oil absorption of commercially available expanded perlite products, measured using the standard methods described below, are shown in Table I. The lowest median particle size (d50) for the product having a blue light brightness higher than 80 is 17.87 microns (sometimes abbreviated “μ”; i.e., μm, or micrometer). The lowest oil absorption for these commercially available expanded perlite products is 182 percent by weight.
TABLE 1d50Blue lightOil AbsorptionProductManufacturer(μm)Brightness(weight %)Harborlite ® 2000Harborlite Corp.58.8483463Harborlite ® 1950SHarborlite Corp.62.4073337Harborlite ® 1900SHarborlite Corp.54.9471346Harborlite ® 1500SHarborlite Corp.52.6469374Harborlite ® 1500Harborlite Corp.50.4581364Harborlite ® 900SHarborlite Corp.54.0070411Harborlite ® 900Harborlite Corp.44.3782355Harborlite ® 800Harborlite Corp.39.6981281Harborlite ® 700Harborlite Corp.38.6681294Harborlite ® 635Harborlite Corp.25.3079255Harborlite ® 500Harborlite Corp.44.1576287Harborlite ® 475Harborlite Corp.28.5077281Harborlite ® 400Harborlite Corp.36.5576285Harborlite ® 300CHarborlite Corp.18.7580226Harborlite ® 200ZHarborlite Corp.19.1875222Harborlite ® 200Harborlite Corp.21.8575213Europerlita ™ 1500Europerlita Espanola, S.A.52.6974326Europerlita ™ 900Europerlita Espanola, S.A.49.5972381Europerlita ™ 700Europerlita Espanola, S.A.46.4571294Europerlita ™ 475Europerlita Espanola, S.A.37.9371239Europerlita ™ 400Europerlita Espanola, S.A.22.9176283Europerlita ™ 350Europerlita Espanola, S.A.18.1374231Europerlita ™ 75Europerlita Espanola, S.A.15.9870218Dicalite ™ 416Grefco, Inc.12.0277185Dicalite ™ 426Grefco, Inc.23.9182183Dicalite ™ 476Grefco, Inc.49.9380241Clarcel Flo ™ 2ACeca S.A.53.0571316Randalite ™ W9Winkelmann Materaria S.r.L.33.9073226Randalite ™ W12Winkelmann Materaria S.r.L.42.3578220Randalite ™ W19Winkelmann Materaria S.r.L.43.0473300Randalite ™ W24Winkelmann Materaria S.r.L.45.2180320Randalite ™ W28Winkelmann Materaria S.r.L.53.8177413Randalite ™ W32Winkelmann Materaria S.r.L.63.4476339Topco ™ #54Showa Chemical Industry Co., Ltd5.4776200Topco ™ #51Showa Chemical Industry Co., Ltd34.2778285Topco ™ #31Showa Chemical Industry Co., Ltd37.9675287Topco ™ #34Showa Chemical Industry Co., Ltd39.7478355Topco ™ #36Showa Chemical Industry Co., Ltd44.3376411Topco ™ #38Showa Chemical Industry Co., Ltd45.5677374Roka Help ™ #419Mitsui Mining & Smelting Co., Ltd19.2977298Roka Help ™ #479Mitsui Mining & Smelting Co., Ltd39.4373281Roka Help ™ #4159Mitsui Mining & Smelting Co., Ltd47.5277344SM 101Samson Co., Ltd.11.6075213SM 201Samson Co., Ltd17.8781357SM 441Samson Co., Ltd37.0379290SM 501Samson Co., Ltd52.2177355SM 601Samson Co., Ltd56.6574350SM 771Samson Co., Ltd60.0275438SM 881Samson Co., Ltd62.1775440SM 901Samson Co., Ltd62.9875433
There is a need for a micronized perlite product with fine particle size, high blue lightness brightness, and low oil absorption for various filler applications.